1. Field of the Invention
The present invention relates generally to conduit couplings. More particularly, the present invention relates to a compact reinforcement to be used in a crimped coupling for high-pressure hose connections such as in an automotive air-conditioning system.
2. Description of the Prior Art
It is generally known in the art relating to flexible conduit couplings to utilize a coupling member having a collar or concentric circular sleeves. The collar, or outer sleeve, is crimped over a hose circumscribing an inner sleeve in order to engage the hose to the coupling member and create a sealed coupling. Generally, to resist the crimping forces, the inner sleeve is made of heavy gauge steel. Unfortunately, heavy gauge steel adds unwanted cost and weight to the coupling assembly.
O-rings and split rings have been used in couplings for sealing and engaging a hose. For example U.S. Pat. Nos. 5,044,671 and 5,096,231 to Chisnell et al. disclose a hose fitting assembly having a resilient sealing member, such as an O-ring or nylon bushing, on the outer periphery of the inner sleeve that sealingly engages the hose to create a sealed coupling. While the sealing members provide a seal to prevent leaks, they do not add any structural benefit to the fitting, nor do they protect the inner coupling member from forces applied to crimp the coupling to the hose.
U.S. Pat. No. 2,250,286 to White discloses a coupling having two concentric circular sleeves. The outer sleeve has a protuberance that contains a split ring that engages the hose with the coupling member when the protuberance is depressed. The depression of the protuberance presses the split ring against the material of the hose and thereby holds the hose firmly between the two sleeves of the coupling. The hose coupling is designed to compress and deform in order to securely engage the hose between the split ring and the inner sleeve of the coupling. Therefore, coupling and use of the split ring to enhance sealing does not in any way prevent the inner sleeve of the coupling from deformation in case of an excessive crimping force.
U.S. Pat. No. 863,745 to Nelson et al. discloses a metal strengthening ring concentrically located between a rubber inner portion and fabric outer portion of a hose. The strengthening ring strengthens an enlarged head portion of the fabric outer portion of the hose, and the coupling is not necessarily crimped at the point where the strengthening ring is located. The placement of the ring prevents expansion of the inner rubber portion of the hose over the strengthening ring and compression of the rubber hose between the ring and the coupling sleeve, that causes damage to the hose and speeds deterioration and failure of the hose and coupling connection. Therefore, the strengthening ring may reinforce the hose, but does not necessarily protect the inner sleeve of the coupling from excessive crimping forces.
More recently, there have been attempts to produce couplings from lightweight materials such as aluminum. However, because of the crimping force necessary to secure the hose to the coupling, reinforcement is required to prevent the weaker aluminum coupling from deforming. Accordingly, U.S. Pat. No. 5,387,016 to Joseph et al. discloses such a tubular coupling fabricated from aluminum that includes a tubular liner having a predetermined length that is press-fit into the tubular connector body. The tubular liner provides structural rigidity and strength to the aluminum connector thereby protecting the coupling from deforming under the crimping force required to connect the tubular connector body to the end of the rubber hose.
Furthermore, Joseph et al. discloses that the tubular liner is formed from a different material than the material of the coupling body to increase the structural rigidity of the body. Therefore, the benefit of using lightweight aluminum for the connector body is countered by the burden of the added weight of the tubular liner. In other words, while the tubular liner of Joseph et al. may add strength, it also adds significantly more weight and cost.
Another problem with the relatively long tubular insert of Joseph et al. is one of beam deflection. Under radial compression, the relatively long tubular liner is weaker and more prone to deflection than a more discrete element of the same cross section would be. That is, when the crimping force is applied to the coupling, the relatively long tubular liner will have a tendency to compress relatively easily because of cumulative deflection along the length of the tubular liner. A more discrete element would undergo relatively minute beam deflection.
Additionally, in an automotive air-conditioning system, the flow of fluid, such as refrigerant fluid, should not be disrupted or it may adversely affect the operation of the air-conditioning system. Accordingly, a disadvantage of the tubular liner disclosed by Joseph et al. is that the reduced inner diameter of the coupling over the entire length of the tubular liner results in a significantly restricted flow of fluid through the coupling.
Further, in a vehicle's air-conditioning system, hose couplings are exposed to a harsh environment where the hose couplings are damaged due to heat and vibrations generated by the vehicle's engine. The harsh engine environment coupled with increased pressure on the hose couplings at the deformed crimped connections has been known to cause prior art couplings to fail prematurely. A discrete reinforcement member in the coupling can provide reinforcement that helps the coupling to overcome the above mentioned shortcomings of the prior art.
Finally, prior art crimped couplings for steel and aluminum couplings have been tested by the applicant of the present invention. Throughout a variety of tests and observation of failed components, it has been concluded that when the crimped connection fails, it fails repeatedly in the same location, independent of whether a steel coupling, an aluminum coupling, or an aluminum coupling with a tubular liner is used. Accordingly, there continues to be a need for a lower cost, lighter weight reinforcement for a hose coupling that will provide support necessary to withstand crimping forces on the tubular body. Finally, the solution must be cost effective, lighter in weight, and not restrict fluid flow through the hose coupling.